Second harmonic generation as a probe of adsorption at colloidal particle surfaces

GEOC 81

R. Kramer Campen1, Eric Borguet2, and James D. Kubicki1. (1) Department of Geosciences, Pennsylvania State University, 801 Deike Building, University Park, PA 16802, (2) Department of Chemistry, Temple University, 201 Beury Hall, 1901 North 13th Street, Philadelphia, PA 19122
Understanding interfacial chemistry at charged colloidal surfaces in aqueous solutions is of interest to a broad range of communities. However, interface specific in situ probes of these environments are lacking. Second harmonic generation (SHG) is a nonlinear optical method capable of providing interface specific molecular insight and appropriate for the study of buried interfaces. In this study we employ SHG as an in situ probe of adsorption at the surface of latex particles in aqueous solution. Specifically, we investigate the adsorption of several dyes at nominally neutral and charged (both positive and negative) particle surfaces. These studies enable us to determine the free energy of adsorption and packing density of these model adsorbates at sufficiently low concentrations to encourage similar analyses of trace nutrients and contaminants on environmentally important particles at field relevant concentrations in the future.